Evaluation of negative energy and mineral balance in periparturient Holstein-Friesian cattle.

摘要

Most cows experience a state of negative energy and mineral balance during the periparturient period. This imbalance is a major problem in the dairy industry and it is more frequently seen in multiparous cattle due to their high milk production. A large amount of fat and protein is mobilized in order to address the energy deficit during the periparturient period. The ability to accurately monitor energetics and electrolytes status using accurate, rapid, and low cost point-of-care instruments will assist in optimizing animal health and productivity.;This dissertation contains three studies that evaluated point-of-care instruments for measuring blood and plasma glucose, beta-hydroxybutyrate, and potassium concentration. The first study, presented in chapter three, evaluated the accuracy of an electrochemical point-of-care meter for measuring blood and plasma glucose concentration in dairy cattle, and characterized the influence of hematocrit and sample temperature on the clinical performance of the meter. A novel equation was developed that accounted for differences in the intra-erythrocyte to plasma ratio of glucose. This equation demonstrated that the algorithm used by the glucometer is optimized for use in human blood and cannot be accurately applied to bovine blood. Sample temperature impacted the measured plasma glucose concentration when the measured value > 160 mg/dL.;The second study, presented in chapter four, evaluated the analytical performance of an electrochemical point-of-care meter for measuring blood and plasma beta-hydroxybutyrate concentration in dairy cattle, and characterized the influence of hematocrit and sample temperature on the clinical performance of the meter. The meter showed non-linearity in bovine blood when true plasma [BHB] > 3.0 mmol/L. The meter is calibrated for use in human blood and a correction equation was developed. Sample temperature had a significant effect on the measured value of plasma beta-hydroxybutyrate concentration when the measured value > 3.0 mmol/L.;The third study, presented in chapter five, evaluated the analytical performance of two ion selective electrode point-of-care meters for measuring plasma, blood, milk, urine and abomasal fluid potassium ion concentrations in dairy cattle. Both meters measured plasma and fat free milk potassium ion concentration ([K+]) 7.3 and 3.6% lower than the indirect ion selective electrode reference method, respectively, and showed excellent performance for measuring potassium ion concentration in abomasal fluid. The ISE methodology is not suitable for measuring [K+] in bovine urine.;The dissertation also contains two more studies. The fourth study, presented in chapter six, characterized the change in plasma calcium concentration around calving. This study identified that plasma calcium concentration is decreased at least 9 hours before calving in multiparous dairy cows fed an acidogenic diet in the late dry period. The final study, presented in chapter seven, characterized the change in skeletal muscle thickness during the first month of lactation as assessed by ultrasonographic measurement and plasma creatinine concentration. Ultrasonographic measurement of longissimus dorsi muscle thickness at the level between 12th and 13th rib provides a promising practical and clinically useful on farm tool for monitoring protein mobilization in periparturient dairy cattle, as well as plasma creatinine concentration. The loss in the BCS during the first month of lactation is about 2/3rds fat (backfat thickness) and 1/3rd muscle (total muscle mass), indicating the ultrasonographic measurement of muscle thickness complements ultrasonographic measurement of backfat thickness as a measure of the rate of fat mobilization.;Collectively, the results presented in this dissertation evaluated the clinical performance of the human electrochemical glucose and beta-hydroxybutyrate point-of-care meter, and two potassium ion selective electrode meters, in cattle, as well as providing an improved understanding of calcium homeostasis and skeletal muscle mobilization in primiparous and multiparous periparturient Holstein-Friesian cattle.